unpin opencv-python (#1262)

http://b/212703016, http://b/284952059

Author: Philmod

Dockerfile.tmpl

@@ -226,8 +226,7 @@ RUN apt-get install -y libfreetype6-dev && \
     /tmp/clean-layer.sh
 
 RUN pip install ibis-framework && \
-    # b/212703016 4.5.4.62 segfault with readtext.
-    pip install opencv-contrib-python==4.5.4.60 opencv-python==4.5.4.60 && \
+    pip install opencv-contrib-python opencv-python && \
     /tmp/clean-layer.sh
 
 RUN pip install scipy \